Miacis Explained

Miacis ("small point") is an extinct genus of placental mammals from clade Carnivoraformes, that lived in North America from the early to middle Eocene.[1] [2] [3]

Description

Miacis was five-clawed, about the size of a weasel (~30 cm), and lived on the North American continent. It retained some primitive characteristics such as low skulls, long slender bodies, long tails, and short legs. Miacis retained 44 teeth, although some reductions in this number were apparently in progress and some of the teeth were reduced in size.

The hind limbs were longer than the forelimbs, the pelvis was dog-like in form and structure, and some specialized traits were present in the vertebrae. It had retractable claws, agile joints for climbing, and binocular vision. Miacis and related forms had brains that were relatively larger than those of the creodonts, and the larger brain size as compared with body size probably reflects an increase in intelligence.

Like many other early carnivoramorphans, it was well suited for an arboreal climbing lifestyle with needle-sharp claws, limbs, and joints resembling modern carnivorans. Miacis was probably a very agile forest dweller that preyed upon smaller animals, such as small mammals, reptiles, and birds, and might also have eaten eggs and fruits.[4]

Classification and phylogeny

History of taxonomy

Since Edward Drinker Cope first described the genus Miacis in 1872, at least twenty other species have been assigned to Miacis. However, these species share few synapomorphies other than plesiomorphic characteristics of miacids in general. This reflects the fact that Miacis has been treated as a wastebasket taxon and contains a diverse collection of species that belong to the stemgroup within the Carnivoraformes.[3] Many of the species originally assigned to Miacis have since been assigned to other genera and, apart from the type species, Miacis parvivorus, the remaining species are often referred to with Miacis in quotations (e.g. "Miacis" latidens). The following table lists the former Miacis species in chronological order of their original description and notes the reassignments to other genera.

Species:Type locality:Status and notes:
M. sylvestris [9] Bridger Formation (Wyoming, USA)now assigned to genus Harpalodon as Harpalodon sylvestris
M. vulpinus [10] Uinta Basin (Utah, USA)Described as Amphicyon vulpinum; later assigned to Prodaphaenus and Miacis; now recognised as synonym of Miocyon scotti
M. uintensis [11] Uinta Basin (Utah, USA)now assigned to genus Prodaphaenus as Prodaphaenus uintensis
M. hargeri [12] Bridger Formation (Wyoming, USA)recognised as close relative to genus Lycarion
M. washakius Bridger Formation (Wyoming, USA)now assigned to genus Neovulpavus as Neovulpavus washakius
M. medius [13] Bridger Formation (Wyoming, USA)now assigned to genus Lycarion as Lycarion medius
M. exiguus [14] Clark's Fork Basin (Wyoming, USA)recognised as close relative to genus Dormaalocyon
M. latidens Clark's Fork Basin (Wyoming, USA)classified as a species of carnivoraform mammals outside of genus Miacis
M. invictus [15] Irdin Manha Formation (Inner Mongolia, China)classified as a species of carnivoraform mammals outside of genus Miacis
M. hookwayi [16] Tapo Canyon (California, USA)classified as a species of carnivoraform mammals outside of genus Miacis
M. gracilis [17] Uinta Basin (Utah, USA)classified as a species of carnivoraform mammals outside of genus Miacis
M. latouri [18] Dormaal (Flemish Brabant, Belgium)now assigned to genus Dormaalocyon as Dormaalocyon latouri
M. lushiensis [19] Shanghuang Quarry (Jiangsu, China)classified as a species of carnivoraform mammals outside of genus Miacis
M. deutschi [20] Clark's Fork Basin (Wyoming, USA)classified as a species of carnivoraform mammals outside of genus Miacis
M. petilus Clark's Fork Basin (Wyoming, USA)classified as a species of carnivoraform mammals outside of genus Miacis
M. winkleri Clark's Fork Basin (Wyoming, USA)now assigned to genus Gracilocyon as type species Gracilocyon winkleri
M. australis [21] Rifle Range Hollow or Blue Cliff Horizon (Texas, USA)now assigned to genus Angelarctocyon as Angelarctocyon australis in family Amphicyonidae[22]
M. cognitus Reeves Bonebed (Texas, USA)now assigned to genus Gustafsonia as Gustafsonia cognita in family Amphicyonidae
M. thailandicus [23] Krabi (South Thailand)now assigned to genus Xinyuictis as Xinyuictis thailandicus
M. boqinghensis [24] Huoshipo, Guojiazhuang Village, Hedi Formation (China)classified as a species of carnivoraform mammals outside of genus Miacis
M. rosei Wyoming, USAnow assigned to genus Gracilocyon as Gracilocyon rosei
M. rundlei [25] Abbey Wood, England, UKnow assigned to genus Gracilocyon as Gracilocyon rundlei
M. solei [26] Dormaal (Flemish Brabant, Belgium)now assigned to genus Gracilocyon as Gracilocyon solei

Phylogeny

The phylogenetic relationships of genus Miacis are shown in the following cladogram:[27] [28] [29] [30]

See also

Notes and References

  1. Book: McKenna . Malcolm C. . Bell . Susan K. . Classification of Mammals Above the Species Level . 16 March 2015 . 1997 . Columbia University Press . New York . 978-0-231-11012-9.
  2. J. J. Flynn (1998.) "Early Cenozoic Carnivora ("Miacoidea")." In C. M. Janis, K. M. Scott, and L. L. Jacobs (eds.) "Evolution of Tertiary Mammals of North America. Volume 1: Terrestrial Carnivores, Ungulates, and Ungulatelike Mammals." Cambridge University Press, Cambridge.
  3. Welsey-Hunt, G. D. . Flynn, J. J. . 2005 . Phylogeny of the Carnivora: basal relationships among the Carnivoramorphans, and assessment of the position of 'Miacoidea' relative to Carnivora . Journal of Systematic Palaeontology . 3 . 1 . 1–28 . 10.1017/S1477201904001518. 2005JSPal...3....1W . 86755875 .
  4. Book: Palmer, D.. 1999 . The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. Marshall Editions. London. 214. 1-84028-152-9.
  5. E. D. Cope (1872.) "Third account of new Vertebrata from the Bridger Eocene of Wyoming Territory." Proceedings of the American Philosophical Society 12:469-472
  6. M. R. Thorpe (1923) "New species of Uinta Carnivora from White River, Utah." American Journal of Science 5(27):218-224
  7. Anthony R. Friscia and D. Tab Rassmussen (2010) „Middle Eocene Carnivoramorpha of the Uinta Basin, Utah”. Annals of Carnegie Museum, vol. 79 (1), pp. 51-63
  8. K. D. Rose, A. E. Chew, R. H. Dunn, M. J. Kraus, H. C. Fricke and S. P. Zack (2012) "Earliest Eocene mammalian fauna from the Paleocene-Eocene Thermal Maximum at Sand Creek Divide, southern Bighorn Basin, Wyoming." University of Michigan Papers on Paleontology 36:1-122
  9. O. C. Marsh (1872.) "Preliminary description of new Tertiary mammals. Part II." American Journal of Science 4(21):202-224
  10. W. B. Scott and H. F. Osborn (1887.) "Preliminary Report on the Vertebrate Fossils of the Uinta Formation, Collected by the Princeton Expedition of 1886." Proceedings of the American Philosophical Society 24(126):255-264
  11. H. F. Osborn (1895) "Fossil mammals of the Uinta Basin. Expedition of 1894." Bulletin of the American Museum of Natural History 7(2):71-105
  12. J. L. Wortman (1901.) "Studies of Eocene Mammalia in the Marsh Collection, Peabody Museum." The American Journal of Science, series 4 12:193-206
  13. W. D. Matthew (1909) "The Carnivora and Insectivora of the Bridger Basin, middle Eocene." Memoirs of the American Museum of Natural History 9:289-567
  14. W. D. Matthew and W. Granger (1915.) "A revision of the Lower Eocene Wasatch and Wind River faunas." Bulletin of the American Museum of Natural History 34(1):1-103
  15. Matthew W. D. & Granger W. (1925.) "New mammals from the Irdin Manha Eocene of Mongolia." American Museum Novitates 198:1–10.
  16. C. Stock (1934) "New creodonta from the Sespe upper Eocene, California." Proceedings of the National Academy of Sciences 20(7):423-427
  17. Clark, John (1939.) "Miacis gracilis, a new carnivore from the Uinta Eocene." Annals of The Carnegie Museum 27, 349-370
  18. G. E. Quinet (1966) "Les mammifères du Landénien continental belge, second tome. Etude de la morphologie dentaire comparée des carnivores de Dormaal." Mémoires de l'Institut Royal des Sciences Naturelles Belges, 158:1-64.
  19. M.-C. . Chow . 1975 . Some Carnivores from the Eocene of China . Vertebrata PalAsiatica . 13 . 3 . 165–168.
  20. P. D. Gingerich (1983) "Systematics of Early Eocene Miacidae (Mammalia, Carnivora) in the Clark's Fork Basin, Wyoming." Contributions from the Museum of Paleontology, University of Michigan 26(10):197-225
  21. E. P. Gustafson (1986.) "Carnivorous mammals of the Late Eocene and Early Oligocene of Trans-Pecos Texas." Texas Memorial Museum Bulletin 33:1-66
  22. Tomiya . Susumu . Tseng . Zhijie Jack . Whence the beardogs? Reappraisal of the Middle to Late Eocene 'Miacis' from Texas, USA, and the origin of Amphicyonidae (Mammalia, Carnivora) . Royal Society Open Science . 3 . 10 . 2016 . 160518 . 2054-5703 . 10.1098/rsos.160518 . 27853569 . 5098994 . 2016RSOS....360518T.
  23. Ducrocq S., Buffetaut E., Buffetaut-Tong H., Helmcke-Ingavat R., Jaeger J.-J., Jongkanchanasoontorn Y. and Suteethorn V. (1992) "A lower Tertiary vertebrate fauna from Krabi (South Thailand)." Neues Jahrbuch fuer Geologie und Palaeontologie Abhandlungen 184(1): 101–122.
  24. X.-S. Huang, Y.-S. Tong and J.-W. Wang (1999.) "A new Miacis (Mammalia Carnivora, Miacidae) from the Middle Eocene of Yuanqu Basin, Shanxi Province." Vertebrata PalAsiatica 37(4):291-299
  25. Jerry J. Hooker . 2010 . "The mammal fauna of the early Eocene Blackheath Formation of Abbey Wood, London" . Monographs of the Palaeontographical Society . 164 . 634 . Palaeontographical Society . 1–162 . 10.1080/25761900.2022.12131814 . 2010MPalS.164....1H . 250702284 . 0269-3445.
  26. Smith . Thierry . Smith . Richard . A New Genus of "Miacid" Carnivoran from the Earliest Eocene of Europe and North America . Acta Palaeontologica Polonica . 55 . 4 . 2010 . 761–764 . 0567-7920 . 10.4202/app.2009.0125 . free.
  27. Book: Flynn . John J. . Finarelli . John A. . Spaulding . Michelle . 2010 . Phylogeny of the Carnivora and Carnivoramorpha, and the use of the fossil record to enhance understanding of evolutionary transformations . Goswami . Anjali . Friscia . Anthony . Carnivoran evolution. New views on phylogeny, form and function . Cambridge University Press . 9781139193436 . 10.1017/CBO9781139193436.003 . 25–63.
  28. Solé . Floréal . Smith . Richard . Coillot . Tiphaine . de Bast . Eric . Smith . Thierry . Dental and tarsal anatomy of Miacis latouri and a phylogenetic analysis of the earliest carnivoraforms (Mammalia, Carnivoramorpha) . Journal of Vertebrate Paleontology . 34 . 1 . 2014 . 0272-4634 . 10.1080/02724634.2013.793195 . 1–21. 2014JVPal..34....1S . 86207013 .
  29. Solé . Floréal . Smith . Thierry . De Bast . Eric . Codrea . Vlad . Gheerbrant . Emmanuel . New carnivoraforms from the latest Paleocene of Europe and their bearing on the origin and radiation of Carnivoraformes (Carnivoramorpha, Mammalia) . Journal of Vertebrate Paleontology . 36 . 2 . 2016 . e1082480 . 0272-4634 . 10.1080/02724634.2016.1082480. 2016JVPal..36E2480S . 87537565 .
  30. Tomiya . S. . Zack . S. P. . Spaulding . M. . Flynn . J. J. . Carnivorous mammals from the middle Eocene Washakie Formation, Wyoming, USA, and their diversity trajectory in a post-warming world . 2021 . Journal of Paleontology . 95 . Supplement S82 . 1–115 . 10.1017/jpa.2020.74. 2021JPal...95S...1T . free . 2433/274918 . free .

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